[gmx-users] Error when performing grompp on lipid bilayer modeled with CHARMM27

[Jianguo Li]

Why not use CHARMM36 FF? It is available in gromacs user contribution website.

If I remember correctly, charmm27 cannot yield correct area/lipid, you need to 
apply surface tension.

Cheeers,
Jianguo


________________________________
From: Jackson Chief <jchiefelk at gmail.com>
To: gmx-users at gromacs.org
Sent: Monday, 5 September 2011 21:20:48
Subject: [gmx-users] Error when performing grompp on lipid bilayer modeled with 
CHARMM27

I want to make a model of a GPCR inserted into lipid bilayer.  I obtained the 
structure file for a solvated POPC bilayer from the CHARMM-GUI site.  I used 
CHARMM27 force field to model the bilayer and pdb2gmx had no problem generating 
the *.gro, *.top, and posre.itp files.  When I perform grompp I receive the 
following warning and error;

"WARNING 1 [file ffnonbonded.itp, line 130]:
  Overriding atomtype HOL"

"ERROR 1 [file bilayer.top, line 271489]:
  No default U-B types"

I though that the issue with creating Urey-Bradley interactions using pdb2gmx 
had been corrected in Gromacs-4.5.4.  Please give me some advice on how to 
proceed further.

Thank you,
Jackson Chief Elk
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